Times change, reasons change, arts are born, arts die.
I just saw a series of documentaries on Hong Kong Martial Arts that makes some interesting points. I suggest you would lears something while watching them.
Of course the topic is simplified for television. Details are not offered as to which arts are extinct, but this is happening.
My friend Ernest Rothrock, Laoshi, has told me the same over a decade ago. His own art, Faan Tzi Ying Jow Pai Northern Eagle Claw, is facing this ame extinction in Hong Kong. However I doubt it is just because children have shorter attention spans. The adult reason is employment. The requirements for making a living take more time away from lives, leaving far less time to train.
So faced with increasing school rent fees, decreasing students with the time to train, arts to fade.
It is interesting the same seems to have occurred on Okinawa.
Prior to 1972 almost all the instruction on Okinawa was for adults. After control of Okinawa returned to Japanese hands, there was an increase in employment and accompanying mainland Japanese practices. Work became the standard of life, and time to train almost became non-existant. The attendance at most dojo decreased dramatically.
Of course things did change, For one thing in Okinawa about 1994 Okinawan teachers with martial backgrounds began a phys. Education program in the schools based on karate. Then teaching karate to children became a large phenomena on Okinawa. Today there are more dojo for children than adults.
Of course this is not well documented.
Change occurs. Instructors who would not share with foreigners may have seen their arts die out, as the Hong Kong story suggests. Some of the arts may have been too vast studies for anyone to attempt in today’s world. Times do change, life and death are part of that.